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Internal temperature reported 100 degrees too high in BK7231T smart plugs with 1.17.501

jrhenk 1962 11
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  • #1 20998439
    jrhenk
    Level 10  

    Hi,
    Finally had time to check out the newest version (1.17.501) and seems a lot has happened since I last checked in! While being busy improving my wifi and getting into OpenWrt I especially appreciated the wifi rsi sensor - I can now have one card with multiple RSI sensors from all over my house to check the effect of wifi configuration changes at a glance, so cool!
    The temperature sensor is also a nice addition but for some reason with my BK7231T based smartplugs it adds 100 degrees to the measurement. After the initial shock I checked and can surely say the plugs are not running at 130 degrees Celsius :) It's these standard AliExpress ones you get for a few bucks in the 3 for 6 dollars section https://www.aliexpress.com/item/1005003640070178.html
    A couple of touch light switches (BK7231N based) are also running 1.17.501 now and they report the temperature correctly.

    Would be great if this could be fixed in one of the next versions. Also: How could I make the temperature a sensor for Home Assistant, too? With all the cheaply produced stuff running 24/7 in my house it would add a bit of peace of mind if I could use this for a warning if they get too hot.

    Let me know if I can add more information about the issue and thanks in advance for looking into it!
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  • #2 20999114
    p.kaczmarek2
    Moderator Smart Home  
    I think it's not calibrated. The temperature readout was submitted by a contributor. We need to figure out a way to get a real value. Maybe recheck source code and measure the real temperature and then use it to adjust the conversion constant.
    Helpful post? Buy me a coffee.
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  • #3 20999130
    jrhenk
    Level 10  

    Thanks for the answer - I'm terrible at opening these plugs without destroying them so I guess I just wait a bit and ignore it for now :) what is interesting however, that with other devices it reports between 25-35 degrees which feels right, with this it reports 125-135 which just seems like +100
  • #4 20999178
    p.kaczmarek2
    Moderator Smart Home  
    Wait, are you saying that it works correctly for other BK7231T?
    Helpful post? Buy me a coffee.
  • #5 20999503
    jrhenk
    Level 10  

    Nope for the plugs with a T chip it is (what I guess) real temperature +100, only for N chips it seems to work correctly - but so far it's very anecdotal evidence. Let me browse through my devices and check whether it's chip or device specific... I think I have an otherwise identical plug with an N chip and a light switch with a T chip
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  • #7 21000588
    jrhenk
    Level 10  

    Oh true! This forum feels so cozy that I sometimes forget that there's a GitHub, too :) but I can fully support the working hypothesis about the issues being limited to the T version. But interesting to learn about the measurable differences between the T and the N - yet I still think it's more about + ~100 instead of being Fahrenheit, since it would mean my chips run at around 60 C which is definitely not the case (pretty much what was pointed out in the GitHub, too)
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  • #8 21000709
    p.kaczmarek2
    Moderator Smart Home  
    We need to know how to convert that "120 degrees" to real temperature, then I can change the code to adjust that.

    For now, maybe I can just add a warning on GUI?
    Helpful post? Buy me a coffee.
  • #9 21001276
    jrhenk
    Level 10  
    I think a little warning would be very nice! The first T device I updated was in the corner of my attic and tbh before I understood what was going on I panicked a little :)


    Added after 10 [hours] 4 [minutes]:

    Wow that was fast, thanks so much! The temperature reading also seems a bit more correct now, in my case from before update 120 to after 52
  • #10 21002199
    p.kaczmarek2
    Moderator Smart Home  
    We are trying to calibrate it a bit, but it seems we also need to raise N temperature by about 10 degrees:
    Thermal image of an electronic circuit board with temperature markings.
    Helpful post? Buy me a coffee.
  • #11 21002769
    jrhenk
    Level 10  
    >>21002199
    cool to see how much work you put into this rather small feature!
  • #12 21014306
    jrhenk
    Level 10  

    @ElektrodaBot How can I send the temperature to home assistant to make it show up like the RSSI?
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Topic summary

✨ The discussion revolves around the internal temperature reporting issue in BK7231T smart plugs running firmware version 1.17.501, which inaccurately adds 100 degrees to the temperature readings. Users noted that while other devices, such as BK7231N-based light switches, report temperatures correctly, the T chip variants consistently show inflated values. Suggestions for calibration adjustments and potential code modifications were proposed, with a consensus that the issue is specific to T chips. Users expressed interest in a warning feature for the GUI to prevent confusion and discussed the possibility of integrating temperature readings with home automation systems like Home Assistant.
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FAQ

TL;DR: On BK7231T devices, internal temperature can read around 120°C; "We need to know how to convert that '120 degrees' to real temperature." Developers are calibrating the conversion to restore accurate values. [Elektroda, p.kaczmarek2, post #21000709]

Why it matters: This helps OpenBK7231 users on 1.17.501 understand the bug, avoid false overheat alarms, and integrate a correct sensor into Home Assistant.

Quick Facts

What’s causing BK7231T to report ~120–135b0C internal temperature?

It’s a calibration issue in the current temperature conversion for the internal sensor. The readout was added by a contributor and lacks proper conversion tuning. The maintainer plans to measure real temperature and adjust a constant in code. “We need to figure out a way to get a real value.” Update to newer builds as improvements land. [Elektroda, p.kaczmarek2, post #20999114]

Is the bug limited to BK7231T, or do BK7231N devices also misread?

Community findings indicate the problem affects T chips only. Reports tie the 100°C error to BK7231T, while BK7231N does not show the same offset in user feedback. If your device is N-based, expect more reasonable values pending minor tuning. [Elektroda, divadiow, post #20999549]

Are BK7231N readings accurate, and by how much could they be off?

Developers observed BK7231N readings might be low and plan to raise them by about 10°C. This suggests N devices are near-correct but benefit from a small positive adjustment. Expect future builds to reflect this calibration change. [Elektroda, p.kaczmarek2, post #21002199]

How far off are BK7231T readings? Do we know the offset size?

Users have seen 125–135°C on BK7231T devices when other devices read 25–35°C in the same environment. That implies an approximate +100°C offset. Treat extreme T readings as a conversion error until calibration lands. [Elektroda, jrhenk, post #20999130]

Did a recent update improve the BK7231T temperature values?

Yes. One user reported the internal temperature dropped from 120°C to 52°C after updating, indicating calibration progress. Keep your firmware current to benefit from ongoing tuning. This statistic demonstrates measurable improvement from newer builds. [Elektroda, jrhenk, post #21001276]

Will the UI warn me if the BK7231T reading is unreliable?

The maintainer proposed adding a GUI warning for the suspicious high value. Check the latest builds for that safeguard and continue to monitor release notes for changes. This helps avoid confusion during calibration work. [Elektroda, p.kaczmarek2, post #21000709]

How can I help calibrate the internal temperature on my device?

Provide a real-world reference so the conversion can be adjusted. “We need to figure out a way to get a real value.” How-To: 1. Measure actual temperature near the device with a trusted thermometer. 2. Note your device’s internal reading and chipset (T or N). 3. Share both in the forum thread for calibration. [Elektroda, p.kaczmarek2, post #20999114]

How do I add the device temperature to Home Assistant?

Use an MQTT Sensor. How-To: 1. Ensure your device publishes temperature to an MQTT topic. 2. In Home Assistant, add an MQTT Sensor that subscribes to that state_topic and set unit_of_measurement to °C. 3. Reload MQTT entities or restart Home Assistant to see the sensor. [MQTT Sensor]

I saw 130b0C on a plugshould I panic?

Don’t panic if it’s a BK7231T on affected firmware. Users observed 125–135°C on T devices while other devices read 25–35°C nearby. That pattern points to a +100°C conversion error, not actual overheating. Verify after updating calibration builds. [Elektroda, jrhenk, post #20999130]

Which plugs are known to show this issue?

A standard low-cost AliExpress smart plug using BK7231T showed the problem. The report came from a device in the “3 for 6 dollars” category. Other T-based plugs may behave similarly until calibration is finalized. [Elektroda, jrhenk, post #20998439]

What firmware version was involved when users first noticed it?

Users reported the +100°C behavior while testing version 1.17.501. If you run that build on BK7231T, expect inflated internal temperature until you update to a corrected release. [Elektroda, jrhenk, post #20998439]

Is this a Fahrenheit vs Celsius mix-up?

No. Community feedback indicates it’s closer to a +100°C offset, not a C/F conversion mistake. “It’s more about + ~100 instead of being Fahrenheit,” since Fahrenheit would imply ~60°C. [Elektroda, jrhenk, post #21000588]

Does the Wi‑Fi RSSI sensor work normally on the same firmware?

Yes. Users called out the RSSI sensor as working well and helpful across multiple devices. It’s unaffected by the internal temperature calibration issue. You can rely on it for network diagnostics. [Elektroda, jrhenk, post #20998439]

What’s the maintainer’s current plan to fix temperatures across T and N chips?

They are actively calibrating conversion. For N chips, they plan to raise readings by about 10°C. For T chips, they’ll adjust the conversion so the reported values match real temperature, based on community measurements. [Elektroda, p.kaczmarek2, post #21002199]
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